A cellular radiotelephone system consists of a number of base stations and radiotelephone handsets. The user receives and places radiotelephone calls through the handset, which is in radio communication with one of the base stations.
A satellite radio communications system, such as the IRIDIUM.RTM. system, has a network of satellites in a low earth polar orbit, each satellite performing the same function as a base station. The satellites transmit and receive signals from a satellite subscriber unit (SSU) to form a radiotelephone system, allowing users to place radiotelephone calls from anywhere in the world to anywhere else in the world.
Unlike cellular systems, the satellites do not remain in the same place with respect to the surface of the earth. Since the satellite could be anywhere in the hemisphere above the user, the SSU's antenna needs to have a gain pattern that covers the hemisphere above the user. Thus, designers have developed an antenna with a hemispherical gain pattern.
In order for an SSU to communicate with any of the possible low earth orbit satellites, the SSU's antenna needs to be oriented in a vertical position with respect to the ground. This orientation must be maintained regardless of whether the user is holding the SSU in his or her right or left hand.
U.S. Pat. No. 5,559,522 describes an antenna positioning apparatus capable of substantially vertical orientation of a radiotelephone antenna with respect to the ground. Although, the antenna positioning system described can be useful in some radiotelephone configurations, it may not operate properly in all, such as configurations wherein the antenna does not include a wedge shaped mating surface. Thus, there is a need for an alternative apparatus that maintains the antenna in a vertical position with respect to the ground when an SSU is transmitting or receiving. Because signals transmitted between a satellite and a SSU have to travel farther distances than signals in a cellular system, there is an additional need for an apparatus that provides a robust RF connection as the SSU's antenna is rotated to an active position with respect to the SSU's handset.